First-ever detection of a toxic chemical pollutant in the atmosphere

The air above Lamont, Oklahoma, has offered up a surprise. Researchers recorded medium chain chlorinated paraffins (MCCPs) drifting overhead, marking the first airborne detection of the industrial pollutant on the continent.

“It’s very exciting as a scientist to find something unexpected like this that we weren’t looking for,” said Daniel Katz, a University of Colorado Boulder chemistry PhD student and study lead.

They made the find with chemical ionization mass spectrometry (CIMS), a technique sensitive enough to spot parts per quadrillion. 

Why the finding surprised chemists

Previous monitoring caught MCCPs in polar air and several Asian cities, yet none had turned up in the Western Hemisphere, so analysts assumed levels here were negligible.

The Oklahoma readings toppled that assumption within hours of the instrument going live. Concentrations peaked around 3 nanograms per cubic meter, thousands of times higher than remote background values.

Daytime spikes and nighttime lulls hinted at daily temperature swings nudging the compounds between air and dusty farm soils. The pattern implied a nearby, ground-level source rather than distant smokestacks.

Atmospheric chemists now must rethink transport models that treated the United States as a blank spot for these contaminants.

Understanding MCCPs – the basics

MCCPs belong to the wider chlorinated-paraffin class used in metalworking fluids, PVC, and flame-retardant coatings.

Their smaller cousins, short chain chlorinated paraffins (SCCPs), were banned for new U.S. production in 2009 after regulators labeled them persistent, bio-accumulative toxins.

“We always have these unintended consequences of regulation, where you regulate something, and then there’s still a need for the products that those were in,” said Eleanor Browne, a CIRES fellow at CU Boulder.

Manufacturers often swapped to MCCPs when SCCPs fell under tighter rules. That substitution created what Browne calls a regulatory “whack-a-mole” problem. 

International negotiators now weigh an outright phase-out. The Stockholm Convention’s expert committee recommended listing MCCPs for global elimination in 2023, and the final vote is set for 2025.

Until that happens, production and trade continue, and ton-scale shipments still cross borders for plastics, paint, and mining lubricants.

From factory floor to fertilizer

How did a metal-shop additive end up over wheat rows? The team points to biosolid fertilizer, the nutrient-rich sludge spun from municipal wastewater.

Studies show more than half of incoming CPs stick to sludge during treatment, turning the material into a chemical reservoir.

“When sewage sludges are spread across the fields, those toxic compounds could be released into the air,” said Katz. Oklahoma farmers routinely spread biosolids to boost soil nitrogen. 

Wind over freshly treated acreage can lift fine particles laden with MCCPs. Once airborne, sunlight warms the mixture, prompting the more volatile molecules to vaporize.

Australian sampling of sludge gives a sense of the stakes, with MCCP levels topping 3,600 nanograms per gram of dry material. Similar numbers in U.S. sludge would supply plenty of fuel for regional air plumes.

Health concerns over MCCPs

Toxicologists have tied CP exposure to liver stress, endocrine disruption, and developmental harm in animal studies.

Human data remain sparse, but blood surveys in industrial towns show body burdens climbing with local emissions.

MCCPs share structural traits with PFAS “forever chemicals,” and they linger in fat tissue for years. That persistence gives them time to move up food webs and to shadow people far from any factory.

Regulators face a data gap: no federal air standard exists, and personal exposure monitoring is rare. The Oklahoma detection now puts pressure on agencies to draft guidelines that match rising public concern.

How the team caught the culprit

The instrument Katz used counted one-second snapshots of everything heavier than nitric acid. Each chlorinated-paraffin molecule creates a fingerprint of carbon, chlorine, and hydrogen isotopes.

Katz noticed patterns that did not belong to known sulfuric-acid clusters, so he pulled out reference spectra and matched the peaks by hand. That sleuthing confirmed at least eighteen MCCP variants, each hovering in the air for part of every day.

Concentrations climbed steeply with temperature, showing a textbook Clausius-Clapeyron relationship. This evidence told the researchers that soil particles act like a chemical sponge, soaking up MCCPs overnight and bleeding them back at noon.

Even rainstorms failed to scrub the plume completely, suggesting a steady replenishment from the ground surface.

What happens next

The team plans year-round fieldwork to watch seasonal swings and to pinpoint hotspots. They will also sample local soils and sludge to track the chemical’s full path from drain to dust.

State lawmakers have already cited the discovery while debating tighter rules on biosolid land application. Similar debates are picking up in other farm states as word spreads among environmental-health circles.

For industry, the Oklahoma data revive questions about replacing one problematic additive with another. Some manufacturers now explore non-chlorinated lubricants and plasticizers to stay ahead of potential bans.

“I think it’s important that we continue to have governmental agencies that are capable of evaluating the science and regulating these chemicals as necessary for public health and safety,” said Katz.

The wider scientific community sees the study as proof that routine monitoring can still pull surprises from the sky. 

The study is published in ACS Environmental Au.

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